Agents from the Tennessee Bureau of Investigation on Sunday began investigating the death of 5-year-old Lucas Michael Dillon.
The severely injured boy was discovered Saturday by authorities in Whitwell at a home at 395 Jewell Lane.
"At this point, we have neither arrested nor charged anyone," TBI spokesman Josh DeVine said in a statement. "We are classifying this as a death investigation until evidence leads us to do otherwise. We are working to determine how the boy sustained his injuries, and to that end, there will be an autopsy, which will give investigators additional information as the case progresses."